Friction Stir Welding of API Grade X65 Steel Pipes

Transcription

1 Friction Stir Welding of API Grade X65 Steel Pipes Zhili Feng*, Russell Steel**, Scott Packer** and Stan A. David* * Oak Ridge National Laboratory, Oak Ridge, TN ** MegaStir Technologies, Provo, UT April, 2005

2 Acknowledgement Research was sponsored in part by the U.S. Department of Energy, Office of Energy Efficiency and Renewable Energy, Industrial Technologies Program under contact DE-AC05-00OR22725 with UT Battelle, LLC. Technical and financial support of MegaStir Technologies.

3 Why FSW of Pipeline Steels Ultra high-strength steels Properties Productivities? Hydrogen issue Weld metal property matching the base metal

4 Material API 5L Grade X-65 steel Common in oil and gas industry for pipelines 0.08C-1.0Mn-0.235Si-0.04Al-0.016Nb C eq = 0.14 ERW Line Pipe OD: (324 mm) Wall thickness: 0.25 (6.35 mm) Base metal properties per mill specification Yield: 67 ksi Ultimate tensile: 77 ksi Elongation: 33%

5 Welding Polycrystalline cubic boron nitride (PCBN) tool Shoulder diameter: 1 Pin length: 0.22 Girth weld Square butt joint configuration No special groove preparation Surface ground before welding Single pass full penetration from OD Welding parameters rpm 4-6 in/min Welding forge force: 6500 lbf Special run-off tab to eliminate the exit hole on the pipe Argon shielding gas from the tool to protect weld from oxidation

6 Field deployable FSW system

7 Hydraulic internal support/fixture

8 Welding movie

9 Finished pipe

10 Finished pipe

11 Microstructure and Mechanical Evaluation (4) Metallographic samples Weld start Exit tab Face for Metallography 3 cross-weld tensile: 4 wide 9 BM Charpy: 5x3 9 HAZ Charpy: 4.5x3 18 WM Charpy: 9x3 Scale: 1:5 1 (OD weld width) Tool rotation: CCW Retrieving Side 9 3 BM tensile: 4 wide Advancing Side x3.14=37.7 Each section: 9 long after metallography samples

12 Mechanical Testing Tensile Room temperature 3 cross-weld tensile: (1-in wide strip) API Base metal at room temperature Orientation: Axial ASTM E8, rectangular flat Full stress strain curve. Yield stress at 0.2% offset plastic strain and at 0.5% total strain Charpy V notch: ASTM E23, 10x5x50 (sub-sized due to wall thickness) side V-notch through thickness 3 repeats at each temperature. Base metal: axial -50, 0, 20C -50, 0, 20C -50, -30, -20,-10, 0, and 20C HAZ Notch Location Weld Notch Location ~ 0.3

13 Tensile properties Base Metal Cross-weld

14 Samples failed outside the weld and HAZ during cross-weld tensile test

15 Charpy V-Notch Impact Test

16 Charpy V-Notch Impact Test ASTM E23 10x5x50 mm, sub-sized All samples showed 100% shear Energy, J Weld HAZ Base Metal Temp, C

17 Weld Cross-Section Macro 2mm

18 The interface is not easily distinguishable under high magnification

19 Evidence of lack of bonding on the root face Relative small ~ 0.15 mm Oxide layer Did not affect the mechanical tensile and impact properties 0.15mm 0.07mm

20 Microstructure Stir zone Base Metal TMAZ

21 Cross-weld section micro-hardness profile Position (mm) Postion (mm) g /2t 1/4t 3/4t 50

22 Summary A portable, field deployable FSW system has been developed for successful welding of X65 pipe Fully consolidated weld joint can be obtained in a single pass Welding speed Microstructure/microhardness The girth show superior tensile and impact properties